The back brakes are very weak on my sons Ranger. I noticed this when attempting to bleed them. The fronts bleed redily with a lot of fluid. The backs would just dribble 3 drops with a full stroke of the brake pedal. This comes as the final in a series of break repairs. I will outline the symptoms and actions I have taken.

Complaint - Mushy brakes that are weak when stopping, though when pushed harder it brakes too hard sometimes causing a skid.

Action - Repaced Master cylinder, bled lines, pads, turned drums and disks.

Complaint - Still mushy brakes, but stopping is smoother. But now no longer feel back-only ABS kick in.

Action - Assumed bleeding not properly done. Perforned a re-do on the bench bleeding, bled front and then tried to bleed the rear. Noticed very restricted flow when bleeding the back on both sides.

I suspected that with only a few drops of fluid per stroke the back brakes also are performing poorly. To test, from 15-20 MPH went hard on the brakes. Front tires skid, backs did not and there was no feel of ABS working. Inspected the rear lines for crimping befor the splitter - They look fine.

Questions:
1. What could cause the rear brakes not to perform?
2. Is there a special bleeding process for rear ABS?
3. Should I suspect problems with the ABS actuator or computer?

RangerDad

 

I may be dating myself here, but . .

Ford trucks (and virtually all other road vehicles) used to have "Brake Proportioning Valves" - I have no idea if your truck has one or not.

But I *can* tell you that it was the specific job of that valve to meter and route the appropriate volume of brake fluid to the appropriate axle (or wheel, depending on the vehicle).

So . . ceratinly I can't say one way or another the role your ABS is playing in this. But my gut tells me:

#1 - that valve is cheaper than replacing the ABS "controller" if you wind up flying blind.

#2 - It is worth seriously taking a look at (if the darned thing even exists in your application) because neither item will be cheap.

HTH.
Mike.

 

Thanks for your response, CTFuzzy. You might be right - I like your 'Flying Blind' analogy, because that is certainly where I am.

Some of the Rangers have rear only ABS. I do not see anything that is called Proportioning Valve in the Haynes repair manual. However, there is something I would call a splitter right over the differential which distributes the hydraulic power to the both rear brakes. If it has a proportioning valve, this is it.

The Haynes repair manual lists and gives a good illistration of my 'RABS II Electro-Hydraulic Valve'. It is electronically connected and has a corresponding RABS II Module installed under the dash.

 

I just replaced my wheel cylinders in the back because I could not loosen the bleeders (one was rusted in, the other leaked around it instead of up the middle). The cylinders themselves were not in good shape either. I replaced them (~$20 each) and the rear shoes and gave everything under the drums a little wire brushing. Then I used a turkey baster to suck out all the fluid from the master resevoir and used a power bleeder to bleed fluid all the way through the entire system. The brakes felt much better. My fluid was black to start out with and I think it was because the wheel cylinders were leaky. Now my fluid is nice and clean.

One problem I had replacing the wheel cylinders were that the lines had 3/16" fittings and the cylinders themselves are 1/4" fittings. I needed some adapters that were available at auto parts stores.

I also highly reccommend a power bleeder for brake bleeding. MUCH easier than pressing the pedal and it makes the job go way easier. It's worth a little wasted brake fluid.

http://www.motiveproducts.com/

The bleeding procedure for the ABS depends on the year. I checked at a local brake shop (they looked it up in their brake book) and my '98 4x4 did not require any special bleeding procedures. You may have to check it out for your year.

-Jim